The present invention is directed to battery testers of the AC current load type, in general, and more particularly, to a battery tester including a circuit for adjusting a threshold voltage potential used for determining a condition of the battery based whether the tester is in a normal or cold test mode, and a circuit for detecting a proper connection to the terminals of the battery under test.
Modern AC current load type electronic battery testers, like the KM4500 manufactured by ACTRON Manufacturing, Inc. under the registered trademark KAL EQUIP, include a microcontroller with embedded software for managing the functions thereof, like keyboard sensing, display driving, and control of the analog circuitry which interface with the battery, for example. Typically, the user enters information of the battery under test using keys on a panel and reads the information through an alphanumeric display which may be of the liquid crystal type, for example. The microcontroller controls the analog circuitry coupled to the battery under test and processes the measured battery signals to determine the battery""s condition under control of the embedded software routines. While very successful, these type testers are considered at the high end of battery testing equipment spectrum due to their sophistication and multi-functional capabilities.
What is needed is a battery tester that is less sophisticated, simple to use and lower in cost to fill a void at the low end of the equipment spectrum. Through the years, some have attempted to fill this gap by offering simple electronic battery testers without utilizing a microcontroller. Examples of these simple electronic testers are found in the following U.S. Patents:
1. U.S. Pat. No. 3,909,708, issued on Sep. 30, 1975 to Champlin and entitled xe2x80x9cElectronic Battery Testing Devicexe2x80x9d;
2. U.S. Pat. No. 4,719,428, issued on Jan. 12, 1998 to Liebermann and entitled xe2x80x9cStorage Battery Condition Tester Utilizing Low Load Currentxe2x80x9d;
3. U.S. Pat. No. 4,816,768 issued on Mar. 28, 1989 to Champlin and entitled xe2x80x9cElectronic Battery Testing Devicexe2x80x9d; and
4. U.S. Pat. No. 5,592,093 issued on Jan. 7, 1997 to Klingbiel and entitled xe2x80x9cElectronic Battery Testing Device Loose Terminal Connection Detection Via A Comparison Circuitxe2x80x9d.
The present invention offers an alternative to these type electronic battery testers which is simple to use, low in cost and provides aspects not found therein.
In accordance with one aspect of the present invention, an electronic battery tester with normal test and cold test modes comprises: a first circuit for applying an AC current load to a battery under test to induce an AC signal across the terminals of the battery; a second circuit for measuring the induced AC signal and converting it to a first voltage potential signal which is a measure of the battery""s internal resistance; means for adjusting said first voltage potential signal to a second voltage potential signal; third circuit for generating a threshold voltage potential signal at a first value when the battery tester is in a normal test mode and at a second value when the battery tester is in a cold test mode; a comparison circuit for comparing said second voltage potential signal to said threshold voltage potential signal to determine a condition of said battery.
In accordance with another aspect of the present invention, an electronic battery tester with terminal connection detection capability comprises: first and second connectors for coupling to positive and negative terminals, respectively, of a battery under test; an electronic tester unit; first and second supply leads coupling the first connector to the electronic tester unit; first and second return leads coupling the second connector to the electronic tester unit; an indicator driven by said electronic tester unit for indicating a connection when the first and second supply leads and first and second return leads are properly connected to the battery under test through the first and second connectors; said electronic tester unit including a circuit governed by said first and second return leads for inhibiting the indicator from indicating a connection when one of said first and second leads are not properly connected to the negative terminal of the battery under test through the second connector.